The present invention relates to apparatuses ensuring separation of foreign objects from a gas flow and more particularly to apparatuses for preventing entry of foreign objects into an aircraft power plant.
An apparatus according to the present invention may be most effectively used on those aircraft which are able to take off and land on airfields which are not adapted to remove foreign objects from a runway. In addition, the invention may also be used to the best advantage on those aircraft the power plant air intakes of which are disposed comparatively close to the surface of earth and are not shielded from the latter by other elements of the aircraft structure.
The invention may also be used on transport means utilizing gas turbine engines with air intakes arranged so that they are liable to entry of foreign objects.
Entry of foreign objects in the air intake may be caused by a whirlwind formed between the surface of an airfield ground and the air intake due to a drop of air pressure in the stream drawn in by the engine.
Another cause responsible for entry of foreign objects may be attributed to throwing up of the latter by the aircraft nose wheel.
Still another cause of entry of foreign objects in the power plant may be associated with gusts brought about in a windy weather or by movement of other aircraft on the airfield.
Entry of foreign objects in a power plant is accompanied by their impact against the blades of a gas turbine compressor, rotating at a high speed. An impact of foreign objects against the compressor blades leads to a substantial decrease in the strength thereof and frequently to destruction of these blades, which in turn reduces the service life of the whole engine. Destruction of the blades may cause an aircraft accident.
Therefore, the prevention of entry of foreign objects into an aircraft power plant makes it possible not only to increase the economy of an aircraft operation but also to avoid an aircraft accident.
Known in the prior art is an apparatus for preventing entry of foreign objects in an aircraft power plant. The apparatus comprises a rotor kinematically associated with a drive. The rotor drive is presented by a separate stage of an engine turbine. The rotor is disposed in an air duct intermediate an air intake and an engine.
The rotor has a centre body with radial blades secured thereon. The blades are installed at an angle to the plane which is square with the longitudinal axis of the rotor. Besides, the known apparatus has a foreign object collection chamber with an opening for entry of these objects.
The rotor blades form an additional pressure stage of the engine compressor. The additional pressure stage is provided with a variable inlet stator and straightening vanes arranged at the exit of air flow from this stage.
The foreign object collection chamber is provided with a branch pipe for exit of air intended to vary the air flow rate through the engine. Mounted in this branch pipe is a flap the control linkage of which is connected with an air flow regulator.
The opening for entry of foreign objects is disposed after an annular duct leading thereto and is also annular in shape. The opening for entry of foreign objects is arranged concentrically with an air duct of the engine compressor after the additional pressure stage thereof and after the annular duct leading to this opening.
In the given case, the apparatus for preventing entry of foreign objects is integrated into the engine construction as its component part. After the additional pressure stage, the air duct is branched off into an annular duct leading to the opening for entry of foreign objects in the collection chamber and an air duct of the compressor, both ducts being disposed concentrically. These concentrically disposed ducts form a certain angle relative to each other (cf. U.S. Pat. No. 3,979,903).
The known apparatus does not generally ensure complete protection of the power plant from entry of foreign objects, inasmuch as the air duct branching off after the additional pressure stage does not necessarily prevent foreign objects from being entrained by the air flow after the additional pressure stage and passed to the compressor.
As the angle between the annular duct leading to the opening for entry of foreign objects and the air duct of the engine compressor after the additional pressure stage is comparatively small, a repeated entrainment of foreign objects by the air flow is quite possible.
Integration of the engine and the apparatus for preventing entry of foreign objects into a power plant in a single unit restricts the field of possible applications of the apparatus and may cause difficulties in its application in those cases when the use of an engine of the given construction is not optimum.
In addition, the known apparatus sets up an increased hydraulic resistance owing to the air duct branching off at a portion after the additional pressure stage.
It is an object of the present invention to provide an apparatus for preventing entry of foreign objects into an aircraft power plant, wherein rotor blades are installed relative to one another and to an opening of a collection chamber for entry of foreign objects so as to ensure a practically complete prevention of entry of foreign objects into the power plant.
It is another important object of the present invention to provide an apparatus for preventing entry of foreign objects into an aircraft power plant, wherein rotor blades are installed relative to one another and to an opening in a collection chamber for entry of foreign objects so as to reduce the hydraulic resistance of the apparatus at those ratings of the power plant operation when there is no need for protection against foreign objects.
It is a further object of the present invention to provide an apparatus for preventing entry of foreign objects into an aircraft power plant, which should be simple in design, inexpensive and not complicated to manufacture.
It is still another important object of the present invention to provide an apparatus for preventing entry of foreign objects into an aircraft power plant, which should improve operation of the power plant at those ratings when there is no danger of entry of foreign objects by reducing the non-uniformity of air pressure and velocity fields in front of the compressor.